Risking of Prospects and Segments
-
Upload
dkobongkaosoblong -
Category
Documents
-
view
217 -
download
0
Transcript of Risking of Prospects and Segments
-
7/23/2019 Risking of Prospects and Segments
1/32
1
Risking of prospects andsegments
-
7/23/2019 Risking of Prospects and Segments
2/32
2
Probability concept Fundamental rules
Probability = 1- RiskP=1.0 means 100% certainty
P=0.0 means 0% certainty
1.0 0.0
0.9 0.1
0.8 0.2
0.7 0.3
0.6 0.4
0.5 0.5
0.4 0.5
0.3 0.7
0.2 0.8
0.1 0.9
0.0 1.0
RISK
PROBABILITY
-
7/23/2019 Risking of Prospects and Segments
3/32
3
Probability concept Multiplication rule.
P=Pa x Pb x Pc x Pd.
Used when estimating theprobability of discovery formapped prospect.
Prospect probability is a product ofseveral independent factors (suchas reservoir, trap, charge and
retention).
-
7/23/2019 Risking of Prospects and Segments
4/324
Probability concept Addition rule.
P=Pa + Pb.
Deal with several outcomes such as
the question of whether oil or gaswill be the dominant phase in theprospect being evaluated.
-
7/23/2019 Risking of Prospects and Segments
5/325
Probability concept Combination rule.
(1-P)=(1-Pa) x (1-Pb).
Deals with interdependency betweenprospects.
-
7/23/2019 Risking of Prospects and Segments
6/326
Risk model Estimate the probability of making
a discoveryMake the volume estimates less
wrong (White, 1993)
Establish risking guidelines prior toassessment
To provide consistency
Attempts to promote objectivity
-
7/23/2019 Risking of Prospects and Segments
7/327
Risk levels
Split into prospect level and playlevel. Play attributes assumed to be common to
all prospects in the play are grouped in theplay level.
Prospect risk factors are assumed to beunique for each prospect and estimates
vary from prospect to prospect.
-
7/23/2019 Risking of Prospects and Segments
8/328
Play and Prospect risk
Retention after accumulation
Migration into the structure
Presence of effective sealTiming of structuring
Presence of structurePresence of mature source rock
Prospect risk factorsPlay risk factors
Presence of effective porosityPresence of reservoir facies
Risk Model
-
7/23/2019 Risking of Prospects and Segments
9/329
Probability of discovery The estimated prospect probability
is not the probability of making adiscovery but:
The probability of finding at leastthe minimum quantity of HC
estimated in our resourceassessment.
CCOP-REP Vung Tau 1996
-
7/23/2019 Risking of Prospects and Segments
10/3210
Probability of discovery The product of major probability
factors Pdisc = Pplay x Pprospectwhere Pplay = Preservoir facies x Pmature source x Ptiming
and Pprospect= Pporosity x Pgeometry x Pseal x Pmigration x
Pretention.
Probability factors are evaluated withrespect to presence andeffectiveness.
-
7/23/2019 Risking of Prospects and Segments
11/3211
Probability of regionallydistributed reservoir facies
0.0 - 0.2Reservoir unit not present in the play area
0.2 - 0.4Presence is based on analog model
0.4 - 0.6Regional distribution of the unit is probable
0.6 - 0.8Found in at least one well; convincing seismic dataclearly indicate a regional distribution of the unit
0.8 -1.0Found in all wells in the play area; facies modeling andseismic data clearly indicates presence of the reservoir
unit in between wells
Quantitativeprobabilityrange
Technical tests criteria
Describes the probability that a regionally
distributed facies that constitute the reservoirinterval in the mapped prospects andunmapped resources exist.
-
7/23/2019 Risking of Prospects and Segments
12/3212
Probability of sufficientmature source rock
0.0 - 0.2Presence of mature source rock is probable
0.2 - 0.4Presence is based on analog model
0.4 - 0.6Wells in play have HC shows/well samples show presenceof source rock & geochemical modeling predicts maturesource rock
0.6 - 0.8Found in at least one well; convincing seismic data clearly
indicate a regional distribution of the unit
0.8 -1.0Commercial production in play area, wells tested moveableHC
Quantitativeprobability
range
Technical tests criteria
Describes the probability that a sufficientmature source rock exists.
-
7/23/2019 Risking of Prospects and Segments
13/32
13
Source rock evaluation
Best done through basin modeling
Factors to be examined
Quality of potential source rock
Type of hydrocarbon generated
Areal and spatial distribution of mature
source rock within play area Poin in time for onset and end of oil
generation
Volume of hydrocarbon generated
-
7/23/2019 Risking of Prospects and Segments
14/32
14
Probability of timing ofstructuring
Describes the probability that thestructures have been present before theend of the hydrocarbon generation.
0.0 - 0.2Unambiguous data suggest that the trap was not inexistecen priori to the end of HC generation.
0.2 - 0.4Unconvincing data indicate that the trap was not present
prior to the end of the HC generation
0.4 - 0.6Based on the available data, it is equally probable that thetrap was in existence prior to the end of the HCgeneration.
0.6 - 0.8Convincing data indicate trap existed before migration
0.8 -1.0Unambiguous data suggest trap existed before start ofmigration
Quantitative
probabilityrange
Technical tests criteria
-
7/23/2019 Risking of Prospects and Segments
15/32
15
Probability of the effective
porosity
0.0 - 0.2Reservoir rock has parameters lower than the minimum0.2 - 0.4Adequate reservoir parameters may exist in trend
0.4 - 0.6Existence of effective reservoir parameters is equallyprobable
0.6 - 0.8Lateral continuity is probable as indicated by seismic, well,and/or outcrop data
0.8 -1.0Identical reservoir rock parameters are found in field ordiscovery in immediate vicinity
Quantitativeprobabilityrange
Technical tests criteria
Describes the probability of the existence of
an effective reservoir facies with reservoirparameters equal to or higher than the
minimum estimate
-
7/23/2019 Risking of Prospects and Segments
16/32
16
Probability of
structure/geometric body
0.0 - 0.2Identical structure proven absent
0.2 - 0.4Structure poorly defined by seismic
0.4 - 0.6A firm conclusion cannot be drawn
0.6 - 0.8Convincing data indicates probable structure
0.8 -1.0Identical structure in immediate vicinity tested
successfully
Quantitativeprobabilityrange
Technical tests criteria
Describes the existence of the mapped
structural/geometrical body with a bulk rockvolume equal or larger than the minimum
value used in the analysis.
-
7/23/2019 Risking of Prospects and Segments
17/32
17
Probability of effective seal
0.0 - 0.2Sealing mechanism proven unsuccessful
0.2 - 0.4Sealing mechanism poorly defined
0.4 - 0.6Presence of seal is equally probable
0.6 - 0.8Same sealing rock unit tested in trend
0.8 -1.0Presence of thick, regionally extensive and effective sealing
Quantitativeprobabilityrange
Technical tests criteria
Describes the probability of an efficient
top, base and lateral seal of thestructure.
-
7/23/2019 Risking of Prospects and Segments
18/32
18
Probability of migration
0.0 - 0.2Trap is not within a migration pathway
0.2 - 0.4Migration path is complicated and tortuous
0.4 - 0.6Available data indicate that it is equally probable that HChave migrated into the trap
0.6 - 0.8Trap is situated within a migration pathway
0.8 -1.0Unambiguous data verify that HC migrated into similar traps
Quantitativeprobabilityrange
Technical tests criteria
Describes the probability of efficient
migration of hydrocarbons from thesource to the mapped structure.
-
7/23/2019 Risking of Prospects and Segments
19/32
19
Probability of retention after
accumulation Evaluates reactivation of faults,
regional uplift and tilting afteraccumulation
0.0 - 0.2Trap has experienced disturbances by tectonic movements
0.2 - 0.4Sealing mechanism after accumulation is poorly defined
0.4 - 0.6Equally probable that the trap has been or has not beenaffected by tectonic movements after accumulation
0.6 - 0.8Overlying sediments were eroded after accumulation
0.8 -1.0No indication of tectonic movement after accumulation
Quantitativeprobabilityrange
Technical tests criteria
-
7/23/2019 Risking of Prospects and Segments
20/32
20
Definition of terms Marginal probability
The chance that at least one field of at leastminimum size exists in the play. This chancereflects the regional, play-specific riskswithin the play
Conditional probability
The chance that the prospect would hold a
field of at least the minimum size oncondition that the play were regionallysuccessful
(D.A. White, 1993)
-
7/23/2019 Risking of Prospects and Segments
21/32
21
Play probability Confirmed play
Probability (P) is 1 Tested and flowed HC to the surface
(technical discovery) Example:
1.0Marginal play probability
1.0Timing of structuring
1.0Presence of reservoir facies
1.0Presence of mature source rock
Probability (Play)Play risk factors
Marginal play probability = 1.0 x 1.0 x 1.0
-
7/23/2019 Risking of Prospects and Segments
22/32
22
Play probability Unconfirmed play
Probability is between 0 and 1Play is not drilled yet or play has no
technical discovery Example:
0.9Marginal play probability
1.0Timing of structuring
1.0Presence of reservoir facies
0.9Presence of mature source rock
Probability (Play)Play risk factors
Marginal play probability = 1.0 x 0.9 x 1.0
-
7/23/2019 Risking of Prospects and Segments
23/32
23
Prospect probability
Conditional probability The chance that the prospect will be an
accumulation on the condition that the play isfavorable to hydrocarbon accumulation (GeoX)
0.512Conditional prospect probability
1.0Retention after accumulation0.8Migration into the structure
1.0Presence of effective seal
0.8Presence of effective porosity
0.8Presence of structure
Probability (Prospect|Play)Prospect risk factors
Conditional prospect probability = 0.8 x 0.8 x 1.0 x 0.8 x 1.0
-
7/23/2019 Risking of Prospects and Segments
24/32
-
7/23/2019 Risking of Prospects and Segments
25/32
25
Unconditional probability Probability of success = Pplay * Pprospect
0.54Dry hole risk
0.46Unconditionalprobability
0.9Marginal playprobability
0.512Conditional prospect
probability
ProbabilityPROSPECT WHOSE PLAYIS NOT CONFIRMED
0.488Dry hole risk
0.512Unconditionalprobability
1.0Marginal playprobability
0.512Conditional prospectprobability
ProbabilityPROSPECT WHOSE PLAYIS CONFIRMED
Unconditional probability = 0.9 x 0.512Unconditional probability = 1.0 x 0.512
Dry hole risk = 1 0.512 Dry hole risk = 1 0.46
-
7/23/2019 Risking of Prospects and Segments
26/32
26
Risk dependency -a probability perspective
Would your estimate ofA2 COS change if youknew the outcome ofdrilling the A1 segment?
If YES, then you implythat there is risk
dependency between A1
A1
A230% COS
20% COSand A2.
Copyright 2004 GeoKnowledge
Shared risk approach to
-
7/23/2019 Risking of Prospects and Segments
27/32
27
Shared risk approach to
modeling risk dependency Consider the segments A1 and A2. Theshared risk approach partitions the chanceof adequacy into ...
P(shared), that captures all chance ofadequacy that is shared between A1 and A2,and ...
Independent conditional probability for A1and A2, given that the shared probability isOK; P(A1|shared) and P(A2 |shared).
Thus ...
P(A1) = P(A1| shared) * P(shared) = 0.3
P(A2) = P(A2| shared) * P(shared) = 0.2
A1
A230%
COS20%COS
Copyright 2004 GeoKnowledge
Geological interpretation of risk
-
7/23/2019 Risking of Prospects and Segments
28/32
28
g pdependency
FULL dependency example, proven play
Geologic Setting:
Deepwater fan in a proven play.
There is a 30% chance that the
reservoir was deposited at A.
If the reservoir is proven at A, then
the chance at B will improve to 67%.
The reservoir cannot be deposited at B
without also being deposited at A.
A B
.30 .20
.10
.70 .50
alDecreasing
Reservoir COADistalProxim
What is probability that sand reached A? 30%
What is the probability that sand reached B, given thatit reached A? .2/.3 = 67%
Shared Shared Probability Independent ProbabilityShared x Independent
Segment Risk P(shared) P(segment | shared)P(segment)
A 1.00.30B .67.20
1 - .70 = .30.70
Copyright 2004 GeoKnowledge
G l i l i t t ti f i k
-
7/23/2019 Risking of Prospects and Segments
29/32
29
Geological interpretation of risk
dependencyPARTIAL dependency example, proven play
What is probability that the system was deposited? 50% (must be riskedseparately)
Given that it was deposited, what is the chance that it is present in A?
.3/.5 = 60% Given that it was deposited, what is the chance that it is present in B?
.2/.5 = 40%
Geologic Setting:
Channel system in a proven play.
There is a 50% chance that the channel was
deposited in this area.
It is more likely to be at A (Channel axis) than
at B (channel margin).
Due to the sinuosity of the channel, it could
have been deposited at B without being
deposited at A. Or it could have been
deposited in the area, but at neither A nor B.
*Total reservoir COA
Chance the channel was deposited = 50%
B
A.20*.30* Axis
Margin
Shared Shared Probability Independent ProbabilityShared x Independent
Segment Risk P(shared) P(segment | shared)P(segment)
A .60.30B .40.20
1 - .50 = .50.50
Copyright 2004 GeoKnowledge
-
7/23/2019 Risking of Prospects and Segments
30/32
-
7/23/2019 Risking of Prospects and Segments
31/32
31
Shared risks in GeoX 5.4 Set at the level of individual risk factors by
enrolling segments in risk dependency groups
System constrains value of shared probabilityaccording to chance of adequacy probabilities
for segments in risk dependency group
GeoX options for defining shared risksbetween segments
Shared Probability
Max Correlation
Play chance
Note: Technically speaking, these are all variationsof the same method.
Copyright 2004 GeoKnowledge
-
7/23/2019 Risking of Prospects and Segments
32/32
32
Organization and Flow